mount.c

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/*
 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <[email protected]>
 *
 * This file is released under the GPLv2.
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#define DEBUG 

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/magic.h>
#include <linux/slab.h>

#include "sysfs.h"


static struct vfsmount *sysfs_mnt;
struct kmem_cache *sysfs_dir_cachep;

static const struct super_operations sysfs_ops = {
    .statfs     = simple_statfs,
    .drop_inode = generic_delete_inode,
    .evict_inode    = sysfs_evict_inode,
};

struct sysfs_dirent sysfs_root = {
    .s_name     = "",
    .s_count    = ATOMIC_INIT(1),
    .s_flags    = SYSFS_DIR | (KOBJ_NS_TYPE_NONE << SYSFS_NS_TYPE_SHIFT),
    .s_mode     = S_IFDIR | S_IRUGO | S_IXUGO,
    .s_ino      = 1,
};

static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
{
    struct inode *inode;
    struct dentry *root;

    sb->s_blocksize = PAGE_CACHE_SIZE;
    sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
    sb->s_magic = SYSFS_MAGIC;
    sb->s_op = &sysfs_ops;
    sb->s_time_gran = 1;

    /* get root inode, initialize and unlock it */
    mutex_lock(&sysfs_mutex);
    inode = sysfs_get_inode(sb, &sysfs_root);
    mutex_unlock(&sysfs_mutex);
    if (!inode) {
        pr_debug("sysfs: could not get root inode\n");
        return -ENOMEM;
    }

    /* instantiate and link root dentry */
    root = d_make_root(inode);
    if (!root) {
        pr_debug("%s: could not get root dentry!\n",__func__);
        return -ENOMEM;
    }
    root->d_fsdata = &sysfs_root;
    sb->s_root = root;
    sb->s_d_op = &sysfs_dentry_ops;
    return 0;
}

static int sysfs_test_super(struct super_block *sb, void *data)
{
    struct sysfs_super_info *sb_info = sysfs_info(sb);
    struct sysfs_super_info *info = data;
    enum kobj_ns_type type;
    int found = 1;

    for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
        if (sb_info->ns[type] != info->ns[type])
            found = 0;
    }
    return found;
}

static int sysfs_set_super(struct super_block *sb, void *data)
{
    int error;
    error = set_anon_super(sb, data);
    if (!error)
        sb->s_fs_info = data;
    return error;
}

static void free_sysfs_super_info(struct sysfs_super_info *info)
{
    int type;
    for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
        kobj_ns_drop(type, info->ns[type]);
    kfree(info);
}

static struct dentry *sysfs_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *data)
{
    struct sysfs_super_info *info;
    enum kobj_ns_type type;
    struct super_block *sb;
    int error;

    info = kzalloc(sizeof(*info), GFP_KERNEL);
    if (!info)
        return ERR_PTR(-ENOMEM);

    for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
        info->ns[type] = kobj_ns_grab_current(type);

    sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
    if (IS_ERR(sb) || sb->s_fs_info != info)
        free_sysfs_super_info(info);
    if (IS_ERR(sb))
        return ERR_CAST(sb);
    if (!sb->s_root) {
        error = sysfs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
        if (error) {
            deactivate_locked_super(sb);
            return ERR_PTR(error);
        }
        sb->s_flags |= MS_ACTIVE;
    }

    return dget(sb->s_root);
}

static void sysfs_kill_sb(struct super_block *sb)
{
    struct sysfs_super_info *info = sysfs_info(sb);
    /* Remove the superblock from fs_supers/s_instances
     * so we can't find it, before freeing sysfs_super_info.
     */
    kill_anon_super(sb);
    free_sysfs_super_info(info);
}

static struct file_system_type sysfs_fs_type = {
    .name       = "sysfs",
    .mount      = sysfs_mount,
    .kill_sb    = sysfs_kill_sb,
};

int __init sysfs_init(void)
{
    int err = -ENOMEM;

    sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
                          sizeof(struct sysfs_dirent),
                          0, 0, NULL);
    if (!sysfs_dir_cachep)
        goto out;

    err = sysfs_inode_init();
    if (err)
        goto out_err;

    err = register_filesystem(&sysfs_fs_type);
    if (!err) {
        sysfs_mnt = kern_mount(&sysfs_fs_type);
        if (IS_ERR(sysfs_mnt)) {
            printk(KERN_ERR "sysfs: could not mount!\n");
            err = PTR_ERR(sysfs_mnt);
            sysfs_mnt = NULL;
            unregister_filesystem(&sysfs_fs_type);
            goto out_err;
        }
    } else
        goto out_err;
out:
    return err;
out_err:
    kmem_cache_destroy(sysfs_dir_cachep);
    sysfs_dir_cachep = NULL;
    goto out;
}

#undef sysfs_get
struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
{
    return __sysfs_get(sd);
}
EXPORT_SYMBOL_GPL(sysfs_get);

#undef sysfs_put
void sysfs_put(struct sysfs_dirent *sd)
{
    __sysfs_put(sd);
}
EXPORT_SYMBOL_GPL(sysfs_put);